1. Field of the Invention
This invention relates to a camera provided with a function which detects a focused image tremble caused by a hand tremble and so on.
2. Description of the Related Art
When an object is photographed by a camera held by the hands of a user, a tremble of a focused image of the object may occur. This is a phenomenon in which an image focused on a film is trembled due to a hand tremble of the user. It can be confirmed by checking a developed picture whether the focused image tremble has occurred or not. Considering that a focused image tremble is mostly caused by the hand tremble of a user, the probability of occurrence of the focused image tremble becomes higher, the longer the focal length of a photographing optical system and the longer the exposure time.
Generally, for a camera requiring 35 mm (millimeter) formatted film, it is known from empirical data that if the shutter speed (exposure time) is faster(shorter) than the reciprocal of the focal length of the photographing optical system, the probability of the occurrence of the tremble in a developed picture is reduced to an extent so as to be negligible.
For example, if the focal length of a photographing optical system is 60 mm (millimeter), this probability becomes extremely small when the exposure time value is shorter than {fraction (1/60)} of a second. Also, if the focal length is 250 mm, the probability becomes extremely small when the exposure time value is shorter than {fraction (1/250)} of a second.
Similarly, in a digital camera provided with an imaging sensor, for example a CCD, the probability of tremble can be controlled by adjusting the relationship between the focal length and the exposure time. Note that, in general, for a digital camera, the focal length as that of the camera for a 35 mm formatted film. However, the actual focal length is determined to be based on the size of the CCD. Further, the exposure time corresponds to a charge store period.
However, the extent of the hand tremble basically depends upon the skill of the user, and the extent can be further affected by the photographing conditions. When a skilled photographer takes a picture, even if a exposure time longer than the reciprocal of the focal length is set, it often happens that a picture in which no tremble occurs is obtained. Further, even if the same user photographs using the same camera under the same conditions, tremble sometimes occurs and sometimes does not occur.
It can not be confirmed until the picture is developed whether the tremble occurred or not. In other words, the user understands that a tremble has occurred, after the photographing has been carried out. Accordingly, there is the problem that, in most cases, the user can not photograph the same object under the same conditions, and a good opportunity for a photograph was lost.
Therefore, an object of the present invention is to obtain a picture in which no tremble occurs, regardless of the skill of the user or the photographing conditions.
In accordance with an aspect of the present invention, there is provided a camera provided with a function which detects a tremble of a focused image comprising: a detector that detects a tremble amount of an optical axis of a photographing optical system; a tremble judging processor that judges, during a photographing period, if the tremble amount detected by the detector exceeds a predetermined permissible tremble amount; and a continuously shooting performance processor that automatically and repeatedly carries out a photographing until the tremble judging processor judges that the tremble amount detected by the detector is less than or equal to the predetermined permissible tremble amount.
Preferably, the camera further comprises a continuously shooting performance stopping processor that stops the automatic performance of photographing carried out by the continuously shooting performance processor even if the amount of tremble detected by the detector continues to exceed the permissible tremble amount.
Preferably, the camera further comprises a number of times setting mechanism that sets the number of times photographing is carried out by the continuously shooting performance processor.
Preferably, the camera further comprises an informing processor which informs a user that the judging processor judges that the tremble amount exceeds the permissible tremble amount.
Preferably, the detector comprises: angular speed sensors that detects an angular speed of the tremble of the optical axis of the photographing optical system; and a calculator of an angular of tremble that calculates angular data of tremble of the optical axis by integrating the angular speed detected by the angular speed sensors.
Optionally, the camera comprises a photosensitive medium as a photographing medium. The photographing period corresponds to an exposure period of the photosensitive medium.
Optionally, the camera comprises an imaging sensor as a photographing medium. The photographing period corresponds to a charge storing period of the imaging sensor. Further, the predetermined permissible tremble amount is set based on the pitch size of pixel of the image sensor.
According to the present invention, until it is confirmed that the amount of the focused image tremble detected during an exposure period is less than or equal to the permissible tremble amount, the photographing is repeated, namely the continuously shooting performance is carried out. Accordingly, it is ensured that a picture, in which no tremble has occurred, can be obtained, being independent of the skill of the user and the photographing conditions.
By providing the number of times setting mechanism, it becomes possible to set the times of the continuously shooting performance based on the extent of the skill of the user, or on an economical standpoint, for example, the amount of film which is able to be used, or on the photographing conditions, and soon. Accordingly, the waste of the photographing medium can be reduced and it is economical.
If the in forming processor is provided, the user is always informed that, a picture in which no tremble has occurred has not yet been obtained, even if the remaining frames of the film or the remaining amount of the photographing medium is limited, or the times of the photographing has reached the times set by the number of times setting mechanism before obtaining a picture in which no tremble has occurred. Accordingly, the user can judge at that time if it is necessary to take a photograph again, so that the opportunity for a photograph is not lost.
Further, by providing the number of times setting mechanism, the continuously shooting performance stopping processor, and the informing mechanism together, when a picture in which no tremble occurs is obtained be fore the number of times of photographing which were carried out becomes equal to the set number of times of photographing, the user is informed that the picture has been obtained, so that further photographing can be stopped depending on the intent of the user. Accordingly, in order to obtain a picture in which no tremble occurs, the number of frames or the capacity of a recording medium can be kept to the minimum, so that it is economical.